Pakistan put into service its new maritime patrol aircraft, based on the Brazilian EMB 145 twin-jet airliner. These will replace their older four-engine P-3C aircraft. Over 1,200 EMB-145s have been built since 1992 and in 1999 Brazil offered a military version, the R-99, for use as an AWACS (Airborne Early Warning Aircraft), maritime patrol or ELINT (electronics intelligence) aircraft. Pakistan is the second customer for the maritime patrol version and plans to buy at least three. These will replace the refurbished American P-3C Pakistan received in 2007. Six are still operational but they are older, four turboprop engine aircraft.
Using twin-jet business or airliner aircraft for military purposes has been increasingly popular. Israel put its first twin-jet AWACS into service in 2006 using a long-range business jet (the 40-ton Gulfstream G550) carrying Israeli-made radar and electronics. The Israeli AWACS came with a Phalcon conformal (built into the lower fuselage) phased array radar, SIGINT equipment (to capture and analyze enemy electronic transmissions) and a communications system that can handle satellite signals as well as a wide array of other transmissions. There are six personnel on board to handle all this gear, plus the flight crew. The Gulfstream G-550 can stay in the air for over twelve hours per sortie, and can fly at up to 51,000 feet. It's a larger version of the Gulfstream G400, which the U.S. Army uses as the C-20H transport. The U.S. Coast Guard, Air Force and Navy also use militarized Gulfstreams.
Australia was the first customer for the Boeing 737 based E-7A “Wedgetail” AWACS and received its first two in 2009. Wedgetail is a militarized Boeing 737 transport. The cruise speed for the 737 is 910 kilometers an hour and the Wedgetail version has a crew of 8-12 pilots and equipment operators, who use the search radar and various other sensors. The 78-ton Wedgetail can stay in the air for more than ten hours per sortie. Wedgetail can refuel in the air and Australian Wedgetails often flew longer missions (14 hours or so) in the Middle East. The limit here was mainly crew fatigue.
Smaller, more powerful and cheaper electronics made smaller twin-jets practical and the most cost effective aircraft for tasks long requiring four-engine turbo-prop or jet aircraft. Even the new U.S. Navy P-8 maritime patrol aircraft is based on the Boeing 767 twin-jet airliner. India is using six Airbus A320 transports, provided by Air India, for conversion to AWACS aircraft. More specifically this is an A319, which is one of the Airbus 320 series aircraft that are similar to the Boeing 737. These twin jet aircraft often replace earlier versions installed in the 1960s B-707 or DC-8 transports or four-propeller airliners like the Electra civilian airliner that first flew in 1954. Only 170 Electras were built but there were nearly four times as many built as P-3s. A few Electras and over 200 P-3s are still in service but will eventually be replaced by twin-jet aircraft.